How flamingos thrive in harsh environments

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Flamingos are a paradox of sorts. They are beautifully plumed from white to light and deep pink to crimson, and they have black flight feathers. They are graceful in flight and while walking, and they can form huge flocks of a million or more that are a sight to behold. As individuals, however, they are odd looking. Their legs and necks seem proportionally too long, and their large bills have a weird shape. Unlike with all other birds, the lower mandible is larger than the upper. The strange-shaped bills, however, are key to their success.

The bills are very thick and bend sharply downward near the middle of their length. When feeding, the head is lowered into the water, the bill points backward, and the top of the upper mandible is closest to the sandy bottom and parallel with it.

Flamingos are the most specialized filter-feeders of all birds. In fact, their method of filtering is unique among birds and, among vertebrates, compares most closely to the baleen whales. Basically, flamingos have a large number of horny, comb-like platelets (lamellae) that function as strainers.

The tongue is thick and moves forward and backward in a groove in the lower mandible, much like the plunger in a syringe. Water enters and leaves the bill along the sides of the two mandibles (gape). When the tongue is drawn back, water is brought in, and when the tongue is pushed forward, water moves out. Food items are removed from moving water by strainers and passed to the gullet.

Straining mechanisms are of two types. In deep-keeled strainers, the upper mandible is long and narrow with a deep “V” shape that fits in the V-shaped lower mandible and pretty much fills the oral cavity. The large surface areas of the sides of the upper and lower mandibles are covered with huge numbers of comb-like platelets that filter small planktonic organisms, such as blue-green algae (cyanobacteria, Spirulina) and diatoms — some the size of a human hair. These flamingos have specialized strainers on the edges of the mandibles that serve as excluders, regulating the size of food that enters.

The upper mandible of shallow-keeled flamingos is neither thick nor V-shaped, like the deep-keeled, and the strainers are fewer and larger. It is designed for larger prey, with size determined by the size of the opening between mandibles (gape). Preferred prey items include brine shrimp (Artemia), larvae of brine flies (Ephedra), and some mollusks and fish.

Where flamingos get their colors

The pink to crimson colors of flamingo plumages comes from beta carotenoids in their diet. Important contributors are brine shrimp and blue-green algae.

Because flamingos occur in such large flocks, finding enough food can be a problem. They solved this dilemma by selecting a habitat that is so extreme, they essentially have no competition. Flamingos utilize highly alkaline lakes and lagoons, most of which are twice as salty as sea water. Many have layers of crystalline salts on the surrounding mud flats. These anaerobic conditions create a stench that is exacerbated by temperatures that can exceed 120°F.

Some waters are caustic. Leslie Brown, while discovering the first nesting ground of the Lesser Flamingo in 1954 (Lake Natron, Tanzania), walked through a shallow soda lagoon and burned his legs so badly he required skin grafts. Flamingos can drink some salt water (they have salt removal glands), but most is too toxic. They either search for freshwater springs or drink from geyser pools, which can be near boiling.

Flamingos are monogamous. They first breed at 3 or 4 years of age, and subsequent breeding occurs every few years. This sporadic cycle is compensated for by a long life expectancy. In February 2013, for example, a dead flamingo was found that had been banded as a chick 50 years earlier.

Flamingos build cylindrical mud nests on mud flats or in shallow water, typically lay one egg, sometimes two, and both sexes incubate for about a month. Nestlings are fed a reddish crop milk right after hatching and, later, form creches of thousands of youngsters fed by their parents. Parents and their young identify each other by sound.

Flamingos are circum-tropical in distribution, sometimes venturing to the subtropics. Shallow-billed flamingos include American Flamingo from the Caribbean and bordering regions (occasionally visiting the southern United States), the Greater from Europe and Africa, and the Chilean from South America. Deep-keeled flamingos include the Lesser from Africa and Andean and James’s (or Puna) from South America.

The extreme habitats of flamingos reduce the threat from terrestrial predators, such as foxes and jackals. Avian predators, including eagles and hawks, are a more serious problem. During the Roman Empire, humans killed huge numbers of flamingos, as emperors believed flamingo tongues to be a delicacy and served them for special dinners. Today the human threat is primarily loss of habitat by drainage and construction of soda ash “mining” plants on the saline lakes.

Flamingos are among the most amazing birds. They thrive under extreme conditions while maintaining a graceful elegance.

 

This article from Eldon Greij’s column “Amazing Birds” appeared in the September/October 2018 issue of BirdWatching. 

 

Originally Published September 19, 2018